Yes, electricity into hydrocarbons... that idea drove me nuts in college. But then I realized that would still require a huge renewable source of ele ctricity, which would not be cheap. Plants and trees, on the other hand, h appily grab carbon dioxide from the air (which is NOT easy to do using arti ficial processes!) and use sunlight to produce material that can fairly eas ily be turned into charcoal. Oh, and they produce a waste product too (foo d). They make charcoal out of coconut shells in the Philippines for exampl e.
But, a "catalytic" process to convert electricity to fuels could look somet hing like this.
H2O => H2 + 1/2 O2 (electrolysis) H2 + CO2 => CO + H2O (reverse water gas shift) n CO + (2n+1) H2 => CnH(2n+2) + n H2O (Fischer-Tropsch) where n = 10 or so for gasoline, higher for diesel)
Only need, oh, $1 billion or so to do it on a large scale. Maybe Obama wou ld be willing to give it to you.
But then I realized that would still require a huge renewable source of e lectricity, which would not be cheap. Plants and trees, on the other hand, happily grab carbon dioxide from the air (which is NOT easy to do using ar tificial processes!) and use sunlight to produce material that can fairly e asily be turned into charcoal. Oh, and they produce a waste product too (f ood). They make charcoal out of coconut shells in the Philippines for exam ple.
ething like this.
ould be willing to give it to you.
Oh, I feel like a college kid again, doing the calcs. =)
Balanced, the net equation becomes
11 H2O + 10 CO2 => 31/2 O2 + C10H22 requiring 31 H2O => 31 H2 + 31/2 O2 to be electrolyzed
One (US) gallon of decane (C10H22) will require 602 moles of water to be el ectrolyzed
From this page:
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html we need 237 kJ/mole of water
This turns out to be 40 kW-hr
So we need 40 kW-hr to produce a gallon of decane (gasoline).
At an electricity rate of $0.10/kW-hr, that's about $4/gallon, or about wha t we pay for gasoline now in California.
Of course this doesn't include any labor, loan amortization on the equipmen t and land, property taxes for the chemical plant, environmental permits, e tc., etc., but when I last did this calc about a decade ago, it didn't mak e any sense at $4/gallon... but it does now... huh.
That may be but the coal companies are claiming it's taking market share. C oal may be cheap but if you consider the distance to market and required in frastructure, like development of rail transport, then it's no longer compe titive. The energy industry can plop down a big NG-fueled cogeneration plan t right at the source and wire it into the system using HVDC relatively qui ckly these days, seems like they're doing it all the time now.
On Thursday, February 21, 2013 10:06:03 AM UTC-5, snipped-for-privacy@yahoo.com wrot e:
SS and other programs would have more money than they know what to do with if they could keep the thieving Congress from grabbing it.
Yep- that's been the problem with this country, good for nothing ignorant r iffraff in positions of authority. Not to worry, now that this calamity of a government is being defunded, a whole bunch of unemployable riffraff will never be managing money again, except possibly in a game of Monopoly.
Ah, but they do it inefficiently -- thinking rather ambitiously, if we harnessed a sizable percentage of insolation (say, 10% land area), we'd only get about 1% of that back as total biomass, or, lemme see,
- Solar irradiation ~173PW
- Land mass 29.2% of surface
- 10% of that is 2.92% or ~5PW
- 1% of that is 50TW
50TWyr ~= 0.44 x 10^6 TWh
Wikipedia says 2008's energy use was 0.14 x 10^6 TWh (fossil, nuclear and renewable), so this is actually within a small factor of today's total use! Of course, most of that is coal and gas, which we don't need to be wasting precious resources on. Without breaking it down further (diesel, gasoline, plastic feedstocks if included, etc.), oil accounts for 0.048 x
10^6 TWh. Which actually means we could supply present demand with 10% of this area, or 1.5 x 10^6 km^2, a bit less than the area of Alaska. Of course, it has to be good arable farmland.
Note that the 1% figure is roughly solar into biomass, so it doesn't matter if you burn the wood, or ethanolize the cellulose, or eat the coconuts; indeed, you have to grow more if you want to eat it. (Give or take a factor of 2, or maybe a few -- last I saw, plants are in the 1-2% range for total solar efficiency into biomass. Obviously, if you get some plants up to 2 or 3%, you've doubled or tripled your global output in this scheme.)
So, since I'm not as concise with figures as you are, in summary -- perhaps we could do it entirely that way, but it would be massive, take all the useful land, and doesn't innovate (i.e., uses current technology, give or take the massive scale!).
The ideal process, of course, would be 100% efficient. But heck, comparing to 1%, even 10% efficiency would be revolutionary.
Existing solar panels are about 10% (neglecting their manufacture, of course), so a quantitative (100% efficient) electrolytic fuel process would be an excellent pairing. Suppose you wired a couple panels to a cell, complete with pumps and tanks and gizmos. Light goes in, fuel comes out!
Or ~100% solar panels, and a crummy 10% process. We can probably come close to that right now:
H2O split is around 70% efficient I think for a typical process (you can get it up around, or even beyond, 100%, but the production rate of endothermic electrolysis is negligible), don't know about gas shift, and I think F-T is around 33% (i.e., for three units of feedstock, you can burn two to synthesize one). So the overall might be 10%-ish.
Solar panels of course are more like 50% for the better theoretical kinds, but existing types aren't going to cut it for water + F-T. F-T can be fed solar power directly, of course, so at least panels would only be necessary for water splitting. There are thermal processes for splitting water also, which AFAIK are more efficient than solar + electrolysis.
It would be really cool if, say, a colloidial catalyst could be made which absorbs light, and reduces carbonate to methanol. Bubble air through the cell to absorb CO2 (as sodium carbonate or whatever), distilling out fresh methanol in a single process. That would be pretty awesome. Carbonate to methanol is more than a few electrons, so doing it on a homogeneous substrate is unlikely; a crazy example idea might be, silicon photodiodes plus nanofluidic electrolysis cells, one for each step, constructed on a microscopic die and dispersed in solution.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com
But coal really is dirty. Particulates, mercury, sulfur, radioactive stuff, ash to be disposed of. Mining and transporting coal is really nasty and dangerous, too. A finished gas well and a pipeline are clean and relatively safe; coal mines and railroads aren't.
Dumping crap into the air, and polluting rivers and such, do damage to everyone and should be paid for. "Clean coal" is in fact non-competitive with ng; even dirty coal is having a hard time competing.
--
John Larkin Highland Technology, Inc
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http://www.highlandtechnology.com
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Pure economics does not account for changes in the value of the commons from one vs. the other.
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Best regards, Spehro Pefhany
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Actually I was reading earlier they've figured out how to get coal to heat up but they can easily sequester the carbon. It's pretty cool - they don't burn the coal, just heat it to a certain temp and it takes off.
If coal plants are phased out as they age, there will be no great economic shocks. Natural gas is an incredible gift. Half the CO2 of coal (if that matters), no particulates, no ash, no mercury, no diesel-burning trains and trucks needed to transport the coal and its wastes.
Fracked NG will probably kill coal on cost alone, at least in the USA. China will more than make up for that, burning hundreds of megatons of Australian coal per year, in very dirty power plants.
So much for Australia being "green."
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--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
Yeah, I kind of like the idea of making fuel from leftover food, because people have to eat anyway.
But you're right, most forms of biomass aren't especially efficient at collecting energy.
Algae is another story. This is a really interesting article.
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Then again, I think that if you have adequate land, sunlight and water, why not just grow crops to feed people? But... if the water is contaminated with hazardous materials, then, sure, algae makes sense.
Biodiesel from algae is much more efficient than biodiesel from vegetable oils. I don't remember just how much more efficient, but I think that article above mentions it.
Makes sense to have critters do as much of the hard work for us as possible. Equipment is expensive.
Carbonate (I'm assuming you mean hydrated carbonate?) to methanol... sounds interesting, but where will you get the carbonate?
Sure, you could do NaOH + CO2 => Na2CO3 or something like that... but it takes energy to make the NaOH! Electrolysis again.
That's not the plan. As it is, if fracking continues to prove economically viable, coal plants would naturally be phased out as they became too expensive to operate. No help from Obama needed.
Let economics do the dirty work. Everyone will be better off for it.
The issue is whether to price the value of dumping wastes into the atmosphere. CO2 aside, sulfur and particulates and mercury hurt people.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
When you remove carbon from the process (as methanol), you implicitly remove carbon*ate* from solution. Leaving you with a (more basic) solution (i.e., containing some hydroxide). You get it for free as part of the continuous process. :)
The full progression is: CO3(2-) (carbonate) -- pull off an electron, proton exchange HCOO(-) (formate) H2CO (formaldahyde) H3COH (methanol) CH4 (methane)
Obviously, the H's and O's change throughout the process, but the important part is convincing it to accept/give up an electron at each step. In aqueous solution, H's and OH's are gratis.
Note that only the first two are acids (carbonic acid and formic acid), and from carbonate to formate, you lose a formal charge, so in that step alone you necessarily free an OH- ion (i.e., you've made one NaOH). Past formaldahyde is just bonus work, but going all the way to methane may not be the most useful step (after all, about half our energy goes to oil, might as well replace that with methanol first!).
Of course, a pH around 9 or 10 isn't exactly friendly to most technologically useful substances. Silicon probably corrodes slowly, and few proteins are stable under those conditions. (Oddly enough, or maybe not, there are a lot of bacteria stable under highly acidic conditions, like the >1% sulfuric acid, plus heavy metals, in acid mine drainage. Base is actually a lot harder for biology to handle than acid is! Speaking of which, don't let ammonia, let alone NaOH, get in your eyes!)
Tim
--
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com
Yes, but more efficient -- evidently, this patent's claim is 58% efficient
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*+828000+gallon+%2F+1+gigawatt+%2F+24+hours (15.6 MJ/L is the figure for heat of combustion of methanol), but it makes no mention of electrode material, coatings, additives or byproducts, which is suspicious (and sadly typical of chemical patents).
All I've seen from carbonate solutions, myself, is oxygen and hydrogen (and other inorganic things, depending on electrode; did you know copper is soluble in sodium carbonate?).
Funnies:
- It's fairly short,
- Fission is emphasized as a resource, but only a few plants (in the US) have been finished since this patent was issued;
- "in the future[,] when available[,] fusion" [sic]!
I recall seeing some recent articles (last couple years) researching this sort of thing in more detail. Obviously, this patent hasn't resulted in anything useful. It's very general, something of an umbrella over the process, specifying only electrolysis be used, but not making any statement over those little things that are ever so important.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://seventransistorlabs.com
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